This invention relates to polypeptide compounds which possess antagonist properties against bombesin or bombesin-like peptides (such as gastrin releasing peptide (GRP), Neuromedin C and the like) hereinafter referred to as bombesin antagonist properties and which are of value, for example in the treatment of malignant diseases in warm-blooded organisms such as man. The invention includes novel polypeptide compounds and processes for their manufacture; novel pharmaceutical compositions containing said polypeptide compounds and processes for the manufacture of medicaments containing them for use in producing a bombesin antagonist effect in warm-blooded organisms such as man.
Bombesin is a tetradecapeptide amide which was first isolated from the skin of the frog Bombina bombina (Anastasi, Erspamer and Bucci, Experientia, 1971, 27, 166). It is known that bombesin is a potent mitogen for mouse Swiss 3T3 fibroblast cells (Rozengurt and Sinnett-Smith, Proc. Natl. Acad. Sci. USA, 1983, 80, 2936) and that it stimulates amylase secretion from guinea pig pancreatic acini (Jensen, Jones, Folkers and Gardner, Nature, 1984, 309, 61). It is also known that bombesin-like peptides are produced and secreted by human small-cell lung cancer (SCLC) cells (Moody, Pert, Gazdar, Carney and Minna, Science, 1981, 214, 1246), that exogenously added bombesin-like peptides can stimulate the growth of human SCLC cells in vitro (Carney, Cuttita, Moody and Minna, Cancer Research, 1987, 47, 821) and that a monoclonal antibody specific for the C-Terminus region of bombesin and GRP can block binding of GRP to its receptors and prevent the growth of human SCLC cells both in vitro and in vivo (Cuttita, Carney, Mulshine, Moody, Fedorko, Fischler and Minna, Nature, 1985, 316, 823).
GRP which has bombesin-like properties is a widely distributed peptide amide containing 27 amino acids isolated from the porcine gut (McDonald, Jornvall, Nilsson, Vagne, Ghatei, Bloom and Mutt, Biochem. Biophys. Res. Commun., 1979, 90, 227) in which the C-terminus amino acid sequence is almost identical to that of bombesin. Neuromedin C is a decapeptide amide, the structure of which is identical to the last ten amino acids in the C-terminus region of GRP, which has been isolated from the canine small intestine (Reeve, Walsh, Chew, Clark, Hawke and Shively, J. Biol. Chem., 1983, 258, 5582). GRP stimulates a variety of biological responses, including the release of gastrin in the systemic circulation. It also functions as a growth factor in 3T3 mouse fibroblasts and small cell lung cancer (SCLC) cell. So GRP has been proposed to play a direct pathophysiological role in the development of SCLC via an autocrine growth mechanism.
The structures of bombesin, Neuromedin C and Carboxyl-terminal nonapeptide of GRP are shown below: ##STR1##
The search for other amphibian bombesin-like peptides led to the isolation of Litorin, a nonapeptide (pGlu-Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH.sub.2)in the skin of frog from Papua, New Guinea which proves to be an extremely potent bombesin analogues (Yasukara et al., Chem. Pharm. Bull., 1979, 27, 492). The studies on bombesin analogues revealed that a minimum segment of the 9 amino acid residues from position 6 to 14 of bombesin possessed the full spectrum of bombesin activity.
Several kinds of bombesin antagonists have now been characterized. Substance P (Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH.sub.2) Seq. ID No. 26 which has slight amino acid sequence homology with bombesin does not inhibit the binding of bombesin and bombesin-like peptides, but Substance P analogues modified by the replacement of several of L-amino acids with D-amino acids such as (D-Arg.sup.1, D-Pro.sup.2, D-Trp.sup.7,9, Leu.sup.11) Substance P and (D-Arg.sup.1, D-Phe.sup.5, D-Trp.sup.7,9, Leu.sup.11) Substance P, (Moody et al., Fed. Proceedings, 1987, 46, 2201) were found to block the secreting of bombesin in pancreatic acinar cells and to antagonize the growth-promoting effects of bombesin in Swiss 3T3 cells. Two types of bombesin antagonists derived from bombesin, for instance, (D-Phe.sup.6, D-Phe.sup.12) bombesin, and [Leu.sup.13 -.sub.psi -Leu.sup.14 ] bombesin (Coy et al., J. Biol. Chem., 1988, 263, 5056 and peptides, 1989, 10, 587) have proved to be potent in vitro and in vivo inhibitors of bombesin response.
Another type of bombesin antagonist revealed by Heimbrook et al., (Bio. Chem., 1989, 264, 11258) is N-acetyl-GRP(20-26) and its analogues, wherein the C-terminal methionine residue is deleted from GRP(20-27) analogues. Coy [J. Biol. Chem.. 264, 1989, 25, 14691] reported that some short chain bombesin antagonists based on Litorin sequence such as [D-Phe.sup.b 6, Leu.sup.13 -.sub.psi -Phe.sup.14 ] bombesin-(6-14) and [D-Phe.sup.6, Leu.sup.13 -.sub.psi -Leu.sup.14 ] bombesin-(6-14) exhibited much more potency than their corresponding parent peptide [Leu.sup.13 -.sub.psi -Leu.sup.14 ] bombesin.
Linear (non-cyclic) bombesin analogues of GRP and amphibian bombesin optionally having a CH.sub.2 --NH non-peptide bond are described in PCT Patent Application WO 90/03980 (and related analogues in WO 91/02746). These analogues, said to act as inhibitors of natural bombesin peptides, have the formula ##STR2## where R.sub.1 and R.sub.2 =H; A.degree. may be deleted; among the many possible amino acids at each position, A.sup.1 may=D-Phe, D-Trp, or D-Nal; A.sup.2 may=Gln; A.sup.4 may=Ala; A.sup.5 may=Val; A.sup.6 may=Gly; A.sup.7 may=His; and W= ##STR3## where R.sub.4 =CH.sub.2 --NH; in some circumstances, Z.sub.1 may=the identifying side chain of Leu, i.e., --CH.sub.2 CH(CH.sub.3).sub.2 ; Z.sub.2 may=the identifying side chain of Cys or Met, i.e., --CH.sub.2 --SH or (CH.sub.2).sub.2 --S--CH.sub.3 ; V=N(R.sub.6)R.sub.7, where R.sub.6, R.sub.7, and R.sub.8 may=H; R.sub.1 and R.sub.2 may=H or COE.sub.1, where E.sub.1 may=C.sub.1-20 alkyl.
Linear peptide analogs of bombesin are also described in EP 0 309 297. These peptides may have C-terminal Met residue and a [CH.sub.2 --NH] pseudopeptide bond between the C-terminal and its adjacent residue.